Detection and Delineation of Sorted Stone Circles in Antarctica

Abstract

Sorted stone circles are natural surface patterns formed in periglacial environments. Their relation to permafrost conditions make them very helpful for better understanding the past climates where they were formed and have evolved and also for monitoring current underlying processes in case circles are active. These metric scale patterns that occur in clusters of tens to thousands of circular elements, can be more comprehensively characterized if automated methods are used. This paper addresses their identification and delineation through the development and testing of a set of automated approaches, namely, template matching, sliding band filter, and dynamic programming. All of these methods take advantage of the 3D shape of the structures conveyed by digital elevation models (DEM), built from ultra-high resolution imagery captured by unmanned aerial vehicles (UAV) surveys developed in Barton Peninsula, King George Island, Antarctica (62°S). The best detection results achieve scores above 85%, while the delineations are performed with errors as low as 7%.

Evidence of Surface Rupture Associated With Historical Earthquakes in the Lower Tagus Valley, Portugal. Implications for Seismic Hazard in the Greater Lisbon Area

“…The images were processed with Agisoft Metashape Professional Software, to build a DSM with a 0.5 cm resolution. Further details on the data processing can be found in Pereira et al (2020).…”

ShetlandsUAVmetry: unmanned aerial vehicle-based photogrammetric dataset for Antarctic environmental research

“…Structure-from-Motion (S f M) photogrammetry techniques have been successfully applied to UAV datasets to generate final georeferenced orthomosaics and topographic products (including a point cloud, 3D mesh, Digital Terrain Model (DTM), or Digital Surface Model (DSM)) by finding common points between the subsequent overlapped captures through triangulation 17 , 18 . In Antarctica, research on the use of UAV-based photogrammetric products has focused on several areas, including: (i) elaboration of detailed basemaps 19 – 21 ; (ii) counting fauna individuals and determining their main morphometric features 22 – 25 ; (iii) mapping vegetation 26 – 28 ; (iv) studying glaciers and ice sheets 29 – 31 ; and (v) monitoring landforms and soils 32 , 33 , many of them are included in Pino & Vieira’s review on the use of UAVs in scientific activities in Antarctica 14 .…”

UAVs for Science in Antarctica

“…Patterned ground: The mapping of patterned ground, namely sorted stone circles, can only be performed by remote sensing through ultra-high resolution datasets. This was achieved with the image mosaics and specially with the elevation datasets of mmcm resolution in Barton Peninsula (King George Island) by Pina et al (2019) [21] and Pereira et al ( 2020) [53]. The automated processing based on machine learning algorithms allowed making adequate identifications and delineations of thousands of individual circles on large datasets, enriching the characterisations and improving the statistics of the traditional field measurements.…”